There have been known semiconductor photodetector devices in which electronic components are mounted in a recess formed in a mounting base called a stem or header, as disclosed, e.g., in Japanese Laid-Open Patent Publication No. 2006-253676. Specifically, in the semiconductor photodetector device disclosed in this publication, a semiconductor photodetector and a preamplifier IC are mounted in a recess formed in the main surface of a stem. The mounting region in the recess where the semiconductor photodetector and the preamplifier IC are mounted is at a lower elevation than the rest of the main surface. This makes it possible to reduce the length of the wires wire-bonded from electrodes of the preamplifier IC to the surface of the stem.
Other prior art includes Japanese Utility Model Laid-Open Patent Publication No. H05-004534 and Japanese Laid-Open Patent Publication No. 2003-134051.
The semiconductor photodetector device disclosed in the above publication has a so-called CAN package structure, and wires are wire-bonded to the top surface of the header, or stem. Since such wire bonding requires a certain amount of surface area on the top surface of the header, the top surface must have a relatively large surface area, or have a relatively low density of electronic components thereon.